Obama urges overhaul of justice system

US President Barack Obama has called for a vast overhaul of the US justice system that would give convicted offenders the vote, curb the use of solitary confinement and end mandatory sentences.

In a week that saw Obama commuting the sentences of 46 drug offenders and which will see him become the first sitting president to visit a federal prison, Obama sketched out a package of justice reforms aimed at reducing the prison population.

The United States, he said, jails as many people as the top 35 European nations combined, with African-Americans and Latinos disproportionately put behind bars for non-violent drug offences.

"Our criminal justice system isn't as smart as it should be. It's not keeping us as safe as it should be. It is not as fair as it should be. Mass incarceration makes our country worse off," he said.

"There are some folks who need to be in jail," Obama said, but he added, in far too many cases the punishment simply does not fit the crime.

Stating he had ordered a review of the use of solitary confinement, and would back scrapping minimum prison terms for non-violent drug offences, Obama received warm applause from members of the National Association for the Advancement of Colored People, a leading rights group.

Obama said there are glimmers of a possible deal between Republicans and Democrats on some reforms this year.

He also called for a shift in popular culture, which tolerates jokes about prison rape.

"We should not be tolerating rape in prison and we should not be making jokes about it in our popular culture. That's no joke."